The invention relates to an implantation device for implanting a sensor element for detecting at least one analyte. Such sensor elements are used, in particular, to determine at least one metabolite concentration in a bodily fluid and/or body tissue. Such metabolites can for example, but not exclusively, comprise blood glucose, lactate, cholesterol or other types of analytes and metabolites. However, alternatively, or additionally, the sensor element can in principle also be used in other fields of analysis, for example in analytic chemistry, particularly in in situ analysis, process monitoring or similar fields.
Many conventional systems for determining analyte and metabolite concentrations are often based on generating a bodily fluid sample, e.g. a drop of blood, and subsequently examining the latter with respect to their analyte contents by using a suitable measurement instrument. By way of example, optical and/or electrochemical measurement methods can be used in this case.
In order to reduce the discomforts of the patients connected to the frequent generation of blood samples, different non-invasive or minimally-invasive techniques for measuring analyte concentrations have been developed. In the following text, determining the blood glucose concentration is discussed without restricting the scope of protection of the invention; however, of course it is the case that other types of analytes and metabolites can, alternatively or additionally, also be detected.
The invasive techniques for determining the analyte concentration are usually based on sensors which can be implanted into body tissue and/or a bodily fluid and which can determine the analyte concentration by optical and/or electrochemical means. In general, optical systems use at least one sensor material which changes at least one property which can be measured optically if one or more specific analytes are present. This property, which can be measured optically can be formed in the most diverse ways, with many different methods, sensor materials and measurement devices being known from the prior art. In principle, all of these known sensor materials can also be used within the scope of the present invention. However, within the scope of the present invention, sensor elements based on electrochemical measurement methods can also be used with the implantation device.
By way of example, WO 01/13783 describes an ocular sensor for glucose, which is designed as an ophthalmic lens. The ocular sensor comprises a glucose receptor as a sensor material, which glucose receptor is marked with a first fluorescent label, and a glucose competitor which is marked with a second fluorescent label (“donor”). The two fluorescent labels are selected such that if the competitor is bound to the receptor, the fluorescence of the second fluorescent label is quenched due to a resonant fluorescence energy transfer (quenching). By monitoring the change in the fluorescence intensity at a wavelength about the fluorescence maximum of the quenchable fluorescent label, the proportion of the fluorescence-marked competitor displaced by the glucose can be measured. This affords the possibility of determining the glucose concentration in the ocular fluid. The measurement can in turn be used to deduce the blood glucose concentration therefrom. Other types of detection are also feasible and known to a person skilled in the art, e.g. a fluorescence detection of the first fluorescent label.
WO 02/087429 describes a fluorophotometer by means of which blood glucose concentrations can be determined by measuring the glucose concentrations from the ocular fluid. The illustrated device is able to measure simultaneously two fluorescence intensities at different wavelengths.
There are different concepts for coupling optical signals into or out of the sensor elements, depending on the tissue type of the tissue into which the sensor element is implanted. In the sensor elements described in WO 01/13783 and WO 02/087429, the tissue layers which cover the implanted sensor are generally transparent in the region of the eye and thus make coupling in and out of light signals possible.
For non-transparent tissue types, WO 2005/054831 A1, for example, describes a sensor element for determining a glucose concentration which uses an optical waveguide. A sensor element is applied to the distal end of the optical waveguide, which sensor element comprises a binding protein which can bind with at least one target analyte. The sensor element furthermore comprises at least one reporter group which is subject to a change in luminescence if the analyte concentrations change. The sensor element optionally comprises reference groups with luminescent properties which do not change significantly if the analyte concentrations change.
U.S. Pat. No. 7,226,414 B2 also describes a glucose sensor device to be implanted within the subcutaneous tissue of an animal body. A sensor material is arranged in a first chamber, with glucose being able to enter into the first chamber from the body tissue. The sensor element furthermore comprises a reference chamber with a reference solution. The use of optical waveguide fibres which connect a detection instrument to the chambers is once again proposed for coupling a read-out instrument thereto.
U.S. 2007/0122829 A1 proposes a system, a device and a method for measuring the concentration of an analyte in a liquid or a matrix. A thermodynamically stabilized, analyte-binding ligand is proposed. In this case, the use of a separate optical waveguide which is in the form of a fibre and coupled to a sensor element is also proposed in turn, which optical waveguide connects a detection instrument with an implanted sensor element.
In particular, a challenge in the case of implantable sensor elements is to uniformly, reproducibly but nevertheless as painlessly as possible implant the sensor elements in the body tissue. Particularly in the case of sensor elements with optical coupling which are wholly or partly covered by a skin section, but also in the case of e.g. electrochemical sensor elements, the implantation depth and the sensor position significantly affect the signal quality. Furthermore, an implantation technique which is as minimally invasive as possible is desirable to ensure an implantation which is as painless as possible, and, subsequently, a removal of the sensor elements which is as painless as possible.